Drill with interchangeable cutting insert

ABSTRACT

A drill includes a substantially cylindrical holder (10) with a longitudinal axis (X) and a transverse axis (Y) perpendicular thereto, a drill tip (12) in which there is a groove (14) running along the transverse axis (Y) with a groove bottom (16) and groove sides (18&#39;,18&#34;), and a cutting insert fitted in the groove having two main cuts (26&#39;,26&#34;) with forwardly adjacent cutting surfaces (32&#39;,32&#34;) and two rear surfaces (30&#39;,30&#34;) opposite a cutting surface on the other side of the transverse axis (Y). The holder has two bores (20&#39;,20&#34;) in a radial plane (R) of the drill, each of which is in the region of a rear surface (30&#39;,30&#34;) of the insert (25) and opens into a groove side (18&#39;,18&#34;). The longitudinal axes (24&#39;,24&#34;) of the drillings (20&#39;,20&#34;) run at an acute angle to the groove side (18&#39;,18&#34;) and the adjacent rear surface (30&#39;,30&#34;) of the insert (25). Stops (50&#39;,50&#34;) projecting from a groove side surface (18&#39;,18&#34;) are arranged in the bores (20&#39;,20&#34;), and at least one of the two stops (50&#34;) can move towards the longitudinal axis (24&#34;) of the bore (20&#34;). Recesses (34&#39;,34&#34;) forming supporting surfaces (38&#39;,38&#34;) corresponding to the stops (50&#39;,50&#34;) are formed in the rear side surfaces (30&#39;,30&#34;) of the insert (25).

TECHNICAL FIELD

The invention pertains to a drill consisting of an essentiallycylindrical holder with a longitudinal axis and a transverse axis thatextends perpendicular to the aforementioned longitudinal axis, a drilltip, inside of which a groove with a groove bottom and groove side wallsis arranged such that it extends along the transverse axis, and acutting insert, in particular consisting of hard metal, that is arrangedin the groove and has two main cutting edges that are arrangedpoint-symmetric to the longitudinal axis and essentially parallel to thetransverse axis, two forwardly adjacent cutting surfaces and two rearside surfaces that are arranged opposite to each respective cuttingsurface on the other side of the transverse axis.

BACKGROUND ART

One such drill is known from the relevant state of the art, namelyGerman U.S. Pat. No. 4,493,596. The drill described in this publicationis provided with fastening elements in the form of screws that hold thecutting insert in the groove of the shaft, namely by being screwed downagainst the groove side walls. For this purpose, the cutting insert isprovided with at least one bore that is arranged perpendicular to thetransverse axis and perpendicular to the longitudinal axis of the drill,with a screw passing through said bore. In this case, the screw head ispreferably realized as a countersunk head that lies in a correspondingcounterbore of the cutting insert in such a way that the screw head isflush with the surface of the cutting insert or countersunk in saidsurface. However, in one preferred embodiment with two bores, the screwis arranged in such a way that the screw head lies in one cuttingsurface, with a threaded screw shaft exiting the rear side surface ofthe cutting insert that is situated opposite to the cutting surface andengaging into a threaded bore arranged in the corresponding groove sidewall. The central axes of the bores provided in the cutting insert foraccommodating the fastening screws as well as the central axes of thethreaded bores provided in the groove side walls for accommodating thethreaded part of the fastening screws are in this case arranged somewhatoffset to one another such that when inserting a screw provided with acountersunk head, as force is exerted that moves the cutting insert inthe direction toward the groove bottom such that it adjoins said groovebottom.

However, the previously described state of the art is associated withthe disadvantage that the screw heads that are arranged in the cuttingsurfaces of the cutting insert impair the direct discharge of the chips.In addition, the bores provided in the cutting insert for accommodatingthe fastening screws weaken the cutting insert, so that the cuttinginsert must have a relatively large extent in the longitudinal directionof the drill in order to compensate for the aforementioned weakening.According to the relevant state of the art, the ratio between thediameter of this drill, i.e., the distance of the adjacent cutting edgesto one another, and the height of the cutting insert is relativelysmall. At a given diameter, this leads to a relatively large extent ofthe cutting insert in the longitudinal direction of the drill andconsequently a weakening of the tip of the drill

U.S. Pat. No. 4,768,901 discloses a drilling tool with two or morecutting edges in which interchangeable cutting elements are fastened incorrespondingly designed recesses in the drill tip by means of screws.In this case, the interchangeable cutting elements are provided withfastening sections that are situated behind the main cutting edge, asviewed in the cutting direction. Each respective fastening section isprovided with a bore that accommodates the screws which engage intothreaded bores that are arranged in the face side of the drill tip andextend parallel to the drill axis. According to this state of the art,the fastening screws are arranged parallel to the drill axis, with aseparate cutting element or a separate cutting insert being provided foreach respective main cutting edge. This state of the art is alsoassociated with the disadvantage that the fastening screws extendthrough bores in the cutting insert, so that bores that limit thegeometric design possibilities and require a correspondingly large sizeof the cutting inserts need to be provided in the cutting elements.

DESCRIPTION OF THE INVENTION

Starting from the relevant state of the art, the present invention isbased on the objective of creating a drill with an interchangeablecutting insert, in which the insert is held in a transversely extendinggroove in the drill tip without requiring bores in the cutting insertand which, with respect to its dimensions, can be realized in such a waythat the drill tip of the holder is weakened as little as possible. Theinvention should have the broadest possible range of applications and,in particular, be suitable for cutting different materials with allconventional drill geometries.

With a drill according to the relevant state of the art, the solution tothe aforementioned objective is characterized by the fact that theholder of the drill is provided with two bores that respectively exitinto one groove side wall, preferably lie in one radial plane of thedrill and are respectively arranged within the region of one rear sidesurface of the cutting insert, with the longitudinal axes of the boresrespectively extending at an acute angle to the respective groove sidewall and the adjacent rear side surface of the insert, that stoppingelements that respectively protrude from one groove side wall arearranged in the bores, that at least one of the two stopping elementscan be moved in the direction of the longitudinal axis of the bore, andthat recesses which form support surfaces that correspond the stoppingelements are arranged or formed in the rear side surfaces of the insert.

In order to realize a point-symmetric shape, it is preferred that thelongitudinal axis of the bores provided in the shaft of the drill foraccommodating the stopping elements be arranged at the same acute angleto the respective groove side wall and the respective adjacent rear sidesurface of the cutting insert, and that the longitudinal axes of thebores have the same distance from the longitudinal axis of the drill orthe holder. In addition, at least one movable stopping element ispreferably realized in the form of a screw, in particular a headlessscrew, with a hexagonal socket.

Due to the design according to the invention, the cutting element neednot be provided with a continuous bore. The shape of the cutting elementis extremely simple, i.e., the processed volume of the cutting elementis minimized. Instead of the bores that, according to the state of theart, extend perpendicular to the transverse axis as defined in thegeneric portion of the claim, the drill according to the invention isonly provided with recesses that form support surfaces, the normal linesto which do not extend perpendicular to the transverse axis, as is thecase with the state of the art, but rather they intersect saidtransverse axis at an acute angle. In cooperation with the stoppingelements that, according to the invention, are arranged in bores in theholder of the drill, this provides a fastening possibility in which thecutting insert is not weakened and consequently can be realized in acorrespondingly flat fashion, i.e., the cutting insert can have smalldimensions in the longitudinal direction of the drill. Consequently, thefastening method according to the invention is suitable for allconceivable cutting edge geometries, namely, even such cutting edgegeometries in which the extent of the cutting edge requires a localreduction in the thickness of the cutting element.

In order to fasten the cutting element, said cutting element is insertedinto the groove and at least one movable stopping element is in a secondstep displaced toward the inside from the outer side of the drill shaft.It is preferred that a stopping element in the form of a headless screwbe used. Since the respective bores exit into one groove side wallwithin the region of one rear side surface of the insert and form anacute angle with the groove side wall, the intersecting point betweenone respective longitudinal axis of a bore and the transverse axis lieson the respective other side relative to the longitudinal axis of thedrill. When tightening the stopping elements or, if only one movablestopping element is provided, the stopping element, a torque is exertedon the cutting insert, with the direction of rotation of said torquebeing identical to that of the torque that is generated during thedrilling process on the cutting edges of the drill due to the reactionforces. As a consequence of the torque generated, both rear sidesurfaces of the cutting insert are pressed against the correspondinggroove side walls within their outer edge regions and adjoin the grooveside walls. The forces exerted upon the cutting edges are absorbed atthis location.

Since the stopping elements are arranged at an angle, a displacement ofone stopping element in the direction of the longitudinal axis of thebore accommodating the stopping element leads to the fact that, due tothe contact between one end face of the stopping element and thecorresponding support surface in the corresponding rear side surface ofthe insert, the cutting insert is displaced in the direction of thetransverse axis by a corresponding vector component until this movementis compensated by a corresponding countermovement of the other stoppingelement. This measure makes it possible to realize a simple centering ofthe cutting insert relative to the longitudinal axis of the drill. Witha point-symmetric arrangement of the stopping elements, which in thiscase preferably lie in one common radial plane, the adjustment isrealized in a particularly simple and reliable fashion.

According to one additional preferred embodiment, it is proposed thatthe support surfaces be realized in planar fashion and limited by anedge in the form of a sector of a circle. With respect to themanufacturing technology, this measure makes it possible to produce thesupport surfaces or the recesses forming said support surfaces in aparticularly simple fashion by means of a milling cutter. In addition,it is also advantageous if at least one recess that forms a supportsurface extend up to the back of the cutting insert, i.e., up to theedge that faces the groove bottom. This measure makes it possible topull the cutting insert out of the groove in the holder thataccommodates the cutting insert without having to entirely unscrew orretract the corresponding stopping element from the groove region. Thismeasure is particularly advantageous if one stopping element is realizedas an immovable stopping element or a stopping element that can be movedalong the axis.

In particular in the latter instance, it is possible to use a stoppingelement that consists of a headless screw, the length of which isshorter than the length of the bore that is arranged in the holder foraccommodating said screw such that a counter sunk screw in the form of ashort headless screw with a hexagonal socket can be arranged in theremaining space that faces the outer side of the drill. This measurecreates a stopping element that need only be adjusted once since itsposition no longer needs to be altered once the cutting insert has beencentered. A recess of the previously described type can be arranged inthe rear side wall of the cutting insert that faces this stoppingelement, namely, a recess that extends up to the edge of the cuttinginsert which faces the groove.

A corresponding recess can also be provided on the opposite side of thecutting insert, i.e., on the other rear side surface. However, thisrecess does not extend up to the groove bottom, so that the cuttinginsert is prevented from falling out once the stopping element, i.e.,the headless screw, has been screwed in. Such an asymmetric design ofthe recesses provides the additional advantage that an erroneousinsertion of the cutting element is not possible as long as the fixed,once adjusted stopping element is not altered.

According to one additional preferred embodiment, it is proposed thatthe longitudinal axes of the bores that accommodate the stoppingelements, e.g., the headless screws, be arranged somewhat offset to thesupport surfaces arranged in the rear side surfaces of the cuttinginsert, so that the end faces of the stopping elements, e.g., the endfaces of the headless screws, only partially cover the support surfacesarranged in the rear side surfaces. This measure insures that theheadless screws comparable stopping elements only contact the supportsurfaces with part of the end face, the relative movement of which isdirected toward the groove bottom while being screwed in. A force isexerted upon the cutting insert in this fashion, with said force pullingthe cutting insert toward the groove bottom such that a defined seat ofthe cutting insert in the groove is attained during assembly.

The design of the drill tip holder according to the invention issuitable for all conventional cutting edges, drill cross sections anddrill tip geometries. This is primarily realized due to the fact thatthe functional surfaces that are required for fastening the insert andarranged on the insert as well as the holder are designed as simply aspossible, and that the volume of the cutting insert as well as thecutting volume on the holder can be minimized in this fashion.

Good results in the cutting of high-strength materials, for example, canbe attained if the shaft of the drill is provided with flutes thatterminate within the region of the cutting surfaces of the cuttinginsert and turn into said cutting surfaces of the cutting insert inflush fashion.

When cutting tenacious and high-strength materials, it is advantageousif the cutting surface be curved in concave fashion. However, it is alsopossible to curve the main cutting edges in such a concave fashion. Inthis case, the fastening geometry can remain unaltered due to the designof the cutting insert holder according to the invention. The cuttingelement is not additionally weakened within the region of the concavesurface due to the transverse arrangement of the bores for accommodatingthe clamping and stopping elements. The proper selection of the anglebetween the bore axis for the clamping and stopping elements and thegroove support surface makes it possible to generate a torque that isdirected opposite to the cutting direction of the drill and consequentlyalready insures a close fit of the cutting element in the slot beginningwith the initial adjustment during which the cutting elements areadjusted and tightened.

The design of the fastening arrangement according to the invention makesit possible to substantially increase the ratio between the diameter ofthe drill, i.e., the distance between the two minor cutting edges, tothe dimension of the cutting insert in the longitudinal direction of thedrill, preferably by a factor of approximately 2. It was demonstratedthat the drill tip holder can be easily used in drilling tools thatallow drilling depth of up to 7 times d.

Due to the fastening of its cutting insert, the drill according to theinvention has substantial reserves regarding its stability.Consequently, it can be easily used for cutting very tenaciousmaterials. In this case, the drill tip angle can be larger than 140°,but should amount to at least more than 130°.

It is preferred that the drill according to the invention be providedwith a coolant channel that makes it possible to convey a coolant, e.g.,a cutting emulsion, from the shaft end of the drill to the drill tip.This coolant channel is preferably arranged in the longitudinal axis ofthe drill, with said coolant channel being divided within the region ofthe drill tip such that two partial channels preferably exit within theregion of the main free surfaces that are part of the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail below with reference to thefigures. The figures show:

FIG. 1: a side view of the holder of a drill according to the invention,

FIG. 2: a top view of the drill tip of the holder according to in FIG.1,

FIG. 3: a section of view taken through the drill tip of the holderalong line III--III in FIG. 2,

FIG. 4: a side view of a cutting insert according to the invention,

FIG. 5: a top view of the cutting insert according to FIG. 4,

FIG. 6: a section of view taken along line VI--VI in FIG. 4,

FIG. 7: a side view of the cutting insert according to the invention inthe direction of the transverse axis,

FIG. 8: a schematic representation of the cutting insert according toFIGS. 2 and 7 which is inserted into the groove of the holder, and

FIG. 9: a section of view taken along line IX--IX in FIG. 8.

BEST MODE FOR CARRYING OUT OF THE INVENTION

FIG. 1 shows the holder 10 of a drill according to the invention. Thisholder has an essentially cylindrical shape with a longitudinal axis Xand a transverse axis Y that is illustrated in FIG. 3 and extendsperpendicular to the aforementioned longitudinal axis. The holder 10comprises a shaft 11 and a drill tip 12.

FIGS. 2 and 3 show that a groove 14 with a groove bottom 16 and thegroove side walls 18', 18" is arranged in the drill tip such that itextends along the transverse axis Y.

The transverse axis Y and the coordinate axis Z that extendsperpendicular to the aforementioned transverse axis form a radial planethat is indicated in FIG. 2. Two threaded bores 20' and 20" thatoriginate from the outer side 22 of the drill shaft and exit into thegroove side walls 18' or 18" are arranged in this radial plane. Thelongitudinal axes 24' and 24" of the bores 18' and 18" are respectivelyarranged at an acute angle to the transverse axis Y or the groove sidewalls 18' and 18". The intersecting points 25', 25" between thelongitudinal axes 24' or 24" and the transverse axis Y are respectivelysituated opposite to the bores on the other side of the longitudinalaxis X of the holder 10.

The reference symbols S' and S" indicate the clamping forces that areexerted on a cutting insert 25 that is accommodated in the groove 14 ina positive fashion via the clamping and stopping elements 50' and 50".In the embodiment shown, the axes 24' and 24" lie in one common radialplane. However, it should be emphasized at this point that thisalignment is not an essential prerequisite for realizing the function ofthe cutting insert holder according to the invention. Thepoint-symmetric arrangement of the clamping and stopping elementsillustrated in the figures is also not absolutely imperative, althoughit provides certain advantages with respect to manufacture, assembly andhandling. FIG. 3 shows that the acute angle formed between the axis 241or 24" and one groove side wall 18' or 18" is chosen in such a way thatthe clamping forces S" and S' transfer a moment M=S" x H onto thecutting insert 25, with said moment being directed opposite to thecutting direction RS of the drill. In other words, the clamping forcescause the cutting insert, during adjustment and fastening tightly, topress against the corresponding groove side walls 18' or 18" with itsrear side surfaces 30' or 30".

FIGS. 4, 5 and 7 show three views of the cutting insert 25 to beinserted into the groove 14. FIG. 5 shows a top view of the cuttinginsert with two main cutting edges 26', 26" that are curved in concavefashion, two adjacent main free surfaces 28' and 28" as well as two rearside surfaces 30' and 30" that extend perpendicular to the plane ofprojection in FIG. 5. The view according to FIG. 4 shows the rear sidesurface 30' and the cutting surface 32" underneath the longitudinal axisX, with said cutting surface being part of the main cutting edge 26' andfacing the observer.

FIG. 4 shows that a recess 34' that extends up to the back 36 of thecutting edge is arranged in the rear side surface 30'. Once the cuttinginsert and the holder are assembled, the back 36 of the cutting edgeadjoins the groove bottom 16. The recess 34' has a planar supportsurface 38' that is manufactured by means of a cylindrical millingcutter as is the case with the side wall of the recess 34' and limitedby an edge 40' in the form of a sector of a circle within a region thatis situated opposite to the back 36 of the cutting edge.

A recess 34" that is illustrated by broken lines is arranged in the rearside surface 30" that is situated opposite to the observer in FIG. 4.This recess forms a support surface 38" limited by an edge 40" in theform of a sector of a circle and a linear edge piece 42".

FIG. 6 shows a section taken along line VI--VI in FIG. 4. The recess 38'is open toward the bottom perpendicular to the plane of projection,while the recess 38" is limited perpendicular to the plane of projectionin FIG. 6.

FIG. 6 also shows that the lines normal to the support surfaces 38' and38" which are illustrated by a dotted-dashed line in FIG. 6 extend at anacute angle to the transverse axis Y. This angle is identical to theangle at which the longitudinal axes of the bores 20' and 20" that areillustrated by dotted-dashed lines in FIG. 3 extend to the transverseaxis Y or the groove side walls 18' and 18".

FIG. 9 shows that stopping elements in the form of headless screws 50'and 50" which engage into the recesses 34' and 34" in the assembledcondition. The headless screws 50' and 50", after insertion of thecutting insert, are screwed into the groove 14 until they adjoin thesupport surfaces 38' and 38". Due to the special arrangement of thelongitudinal axes 24' and 24" of the bores 20' and 20", the headlessscrews turn the cutting insert shown in FIG. 9 in the clockwisedirection, i.e., in the same direction as the cutting reaction forcesthat are indicated by the arrows and act on the main cutting edges 26'and 26". This causes the rear side surfaces 30' and 30" of the cuttinginsert to adjoin the corresponding groove side walls 18' and 18" withinthe outer region of the drill diameter such that the reaction forcesthat act on the main cutting edges 26' and 26" are withstood.

FIG. 9 also shows that the longitudinal axes 24' and 24" of the bores20' and 20" are arranged at a somewhat greater distance from one anotherthan the normal lines 39' a and 39" a to the support surfaces 38' and38" (cf. FIG. 6), so that the end faces 52' and 52" of the headlessscrews 50', 50" only partially cover the support surfaces 38' and 38" ofthe cutting insert 25. This measure insures that a relative movementbetween the end faces of the headless screws that are provided with aright-handed thread and the respective support surface takes place whileinserting said headless screws. In FIG. 9, this relative movement isdirected downward in the direction of the longitudinal axis of the drillwhich extends perpendicular to the plane of projection, so that thecutting insert 25 is pressed against the groove bottom 16 with its back36. In addition, it is possible to adjust or center the cutting insert25 in the direction of the Y-axis by unscrewing one of the two headlessscrews 50' and 50" while screwing in the other headless screw. Once thecentering or adjusting of the cutting insert is completed, one stoppingelement is secured by means of the counter[sunk] screw. This stoppingelement then cooperates with the recess 38' that extends up to the endface 36, so that this fixed stopping element can continuously remaininside the holder. This results in an asymmetric design of the cuttinginsert that consequently can only be inserted into the holder if it isproperly oriented.

FIG. 9 elucidates one additional special feature of the object of theinvention. This figure shows that the support surfaces 38' and 38" are,relative to the axes 24' and 24", arranged in such a way that thesurface contact between the face sides of the headless screws 50' and50- and the corresponding support surfaces 38' or 38" essentially onlytakes place on one side of the screw axes 24', 24". This means thatfrictional forces that are directed toward the bottom 16 of the grooveare generated between the headless screw and the cutting insert duringadjustment and clamping of the cutting insert. Consequently, a firmaxial contact of the cutting insert in the bottom of the slot is insuredduring the adjustment and clamping process.

In the embodiment shown in the figures, the headless screw 50' issubstantially shorter than the headless screw 50" such that anadditional counter[sunk] screw 55 can be accommodated in the bore 20'.The counter[sunk] screw 55 is also realized with a hexagonal socket.After centering the cutting insert, the position of the headless screw50' can be secured by tightening the counter[sunk] screw 55. Should itbecome necessary to replace the cutting insert 25, one need only loosenthe headless screw 50 and unscrew it to such an extent that it no longerprotrudes into the region of the groove 14. Since the recess 34' isrealized in such a way that it is open in the direction toward thegroove bottom 16 or the back 36 of the cutting insert, the cuttinginsert can be pulled out of the groove in the direction of the X-axiswithout having to loosen the headless screw 50' and the counter[sunk]screw 55.

on the other hand, the correspondingly designed recess 34" insures thatthe insert 25 cannot fall out of the groove 14 if the headless screw 50"is inserted.

The fastening elements which, according to the invention, are realizedin the form of stopping elements or headless screws, engage on therespective rear side surfaces 30', 30" of the insert 25 such that boresthat pass through the insert 25 can be eliminated. FIGS. 4 and 5 showsthat it is possible to choose large ratios of the distance between twominor cutting edges 27' and 27" (=D) to the total dimension t of thecutting insert 25 in the direction of the X-axis for the cutting insertaccording to the invention. This ratio which is influenced by the tipangle amounts to approximately 2. The ratio D/t*, in which t* indicatesthe axial length of the guide diameter, can be increased by a factor of3.5.

FIG. 1 shows that the holder 10 or the shaft 11 of the drill can beprovided with a coolant channel 60 that is divided into two partialchannels 62', 62" within the region of the drill tip 12. These twopartial channels 62' and 62" respectively exit into one main freesurface of the drill within the region between one respective flute 64",64' and one respective bore 20', 20".

The drill according to the invention represents a drill with aninterchangeable cutting insert which can be fabricated very easily withrespect to the manufacturing technology, in which the cutting insertweakens the drill tip of the holder less intensely than in drill designsdisclosed so far and consequently is more stable, and in which arequired interchange of the cutting insert can be carried out in asimple and rapid fashion.

It goes without saying that modifications of the previously describedembodiment are possible without deviating from the basic idea of theinvention. The cutting insert is, for example, not limited to apoint-symmetric design. It is, in principle, conceivable that thecutting edges extend differently although one particular advantage ofthe invention is attained if the thickness of the cutting insert isreduced within the region of the rake due to the specific extent of thecutting edges. In addition to hard metals, ceramic or cermet materialscan also be used as materials for a the cutting insert. The cutting edgeplate can be realized as a ground plate or simply as a sintered andconsequently more inexpensive plate. The drill according to theinvention is used for a drilling depth up to 7.5×d, where d representsthe drill diameter.

We claim:
 1. A drill, comprising:a cylindrical holder having alongitudinal axis and a transverse axis that extends perpendicular tosaid longitudinal axis, a drill tip inside of which a groove with agroove bottom and groove side walls is formed such that said grooveextends along the transverse axis, and a cutting insert formed of a hardmetal, said insert being located in the groove and having two maincutting edges that are arranged point-symmetric to the longitudinalaxis, forwardly adjacent cutting surfaces and two rear side surfacesthat are arranged opposite each respective cutting surface on the otherside of the transverse axis wherein:the holder is provided with twobores that respectively exit into said groove side walls, said boreslying in one radial plane of the drill and being respectively arrangedwithin a region of one of said rear side surfaces of the insert, andlongitudinal axes of said bores respectively extending at an acute anglewith respect to the respective groove side walls and the rear sidesurfaces of the insert, clamping and stopping elements are providedwhich respectively protrude out of one of the groove side wall and arearranged in the bores, at least one of the two stopping elements are oneof movable and adjustable in the direction of the longitudinal axis ofthe bore, and recesses that form support surfaces that correspond to thestopping elements respectively are one of provided in and formed in therear side surfaces of the insert.
 2. A drill according to claim 1,wherein the bores extend at the same acute angle with respect to therespective groove side wall and the adjacent rear side surface of theinsert.
 3. A drill according to claim 2, wherein the longitudinal axesof the bores are positioned the same distance from the longitudinal axisof the holder of the drill.
 4. A drill according to claim 1, wherein atleast one of said stopping elements comprises a screw.
 5. A drillaccording to claim 4, wherein the screw comprises a headless screw witha hexagonal socket head.
 6. A drill according to claim 1, wherein atleast one of the support surfaces comprises a planar surface.
 7. A drillaccording to claim 6, wherein the planar support surface has a linearedge and an edge in the form of a sector of a circle, and wherein acylindrical wall that extends perpendicular to the edge in the form of asector of a circle and forms the second wall of the recess is situatedadjacent the perpendicular edge.
 8. A drill according to one of claims 6or 7, wherein the recess extends up to the edge of the cutting insertthat faces the groove bottom.
 9. A drill according to claim 1 whereinthe stopping elements comprise a headless screw and a countersunk screwthat secures said headless screw.
 10. A drill according to claim 1,wherein the recesses arranged on the rear side surfaces of the cuttinginsert and the support surfaces formed by the recesses are arrangedoffset relative to the bores such that the end faces that extendperpendicular to the longitudinal axes of the stopping elements and thesupport surfaces only partially overlap.
 11. A drill according to claim1, wherein the main cutting edges are curved in a concave fashion.
 12. Adrill according to claim 1, wherein the shaft of the drill is providedwith two flutes that extend away from the drill tip.
 13. A drillaccording to claims 11 or 12, wherein the cutting surfaces of thecutting insert are curved in a concave fashion and turn into flutes. 14.A drill according to claim 1, wherein the diameter of the drill isbetween 10 and 50 mm.
 15. A drill according to claim 1, wherein theratio of the diameter of the drill to the total dimension of the cuttinginsert in the longitudinal direction of the drill is approximately 2.16. A drill according to claim 1, wherein the ratio of the diameter ofthe drill to the axial length of the guide diameter of the cuttinginsert is increased by a factor of 3.5.
 17. A drill according to claim1, wherein the tip angle is greater than 130°.
 18. A drill according toclaim 1, wherein a coolant channel is formed in the holder.
 19. A drillaccording to claim 18, wherein the coolant channel is branched.
 20. Adrill according to claim 19, wherein the coolant channel extends in thelongitudinal axis of the drill, and said coolant channel is divided intotwo partial channels within the region of the drill tip, with saidpartial channels exiting into the respective main free surface that ispart of the holder within the region between one respective flute andthe respective bores of the stopping elements.
 21. A drill according toclaim 2, wherein the forces transmitted on the cutting insert by theclamping and stopping elements generate a torque that is directedopposite the cutting direction of the drill.